There are numerous identical threads already active on this topic, however...
4.7 is the largest I would change too, the 5c range will no doubt continue the current size format, at least for a further year after the 6 is launched just with 5s spec no doubt. The one thing I would want is better battery life, especially from the larger phone if it were produced as it's already an issue for the majority of users.
4.7!!!!!! I really like the 4inch display and apple better keep it. Love how I can use it with one hand. So as of right now I want a 4 inch display. But if apple as a 4 inch and a 4.7 inch then maybe I would like the 4.7 inch if I could hold it in one hand i need to see it. If apple want to keep everyone happy then this is what they should and better do!
iPhone 4 inch
iPhone 4.7 inch
iPhone 5.7 inch
BUT they all need to have the same specs!!!! Do you hear me apple THEY ALL NEED TO HAVE THE SAME SPECS that's important!!
I really like the current 4" size, but wouldn't be opposed to 4.5-4.7" as long as the device size didn't increase dramatically.
But if there were multiple sizes, as others have said, please let the specs be the same!
If the ip6 is phablet sized I'm not touching that generation. Half the reason I switched back was I was sick of premium smartphones getting bigger and bigger.